The present invention relates generally to leads implanted in the heart and for conducting electrical signals to and from the heart. More particularly, it pertains to insulation for an endocardial lead.
Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the ventricular epicardium. Permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. A lead may be positioned in the ventricle or in the atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously.
Leads provide the electrical connection between the pulse generator and the heart tissue which is to be excited. Since the lead is disposed in body fluid and is disposed within the patient for long periods of time, electrical insulation of the lead is important. One approach to providing electrical insulation is to provide a lead body of silicone. However, the silicone provides limited abrasion resistance. During placement of the lead, the tip of the lead and lead body travels intravenously through veins and the heart. While traveling through the veins, the lead body may experience resistance from the lead body rubbing against the wall of the vein or the helix at the tip of the lead may snag or attach to the side wall of the vein. This is undesirable as it may cause damage or other complications to a patient during implantation of the lead. In addition, for leads having multiple legs or when multiple leads are implanted, it is important that the lead bodies do not adhere to one another after placement of the lead within the patient.
Accordingly, there is a need for a lead which allows for positioning through a passage, such as a vein or artery, without substantial resistance from the wall of the vein or artery. What is also needed is a lead with improved abrasion resistance, which also provides electrical insulation for the lead.
A lead has a flexible lead body which extends from a proximal end to a distal end. The distal end of the lead body includes one or more legs. Optionally, the lead is coupled with a pulse generator. The lead body has a conductor coupled with an electrode. At least a portion of the flexible lead body includes polymers of vinylidene fluoride, or polymers of vinylidene fluoride and silicone rubber in multiple layers. Optionally, the polymers of vinylidene fluoride comprises a homopolymer, a copolymer, or a terpolymer. The poly (vinylidene fluoride), in one embodiment, comprises a heat shrunk layer of insulation.
A method includes increasing the abrasion resistance of a lead assembly having a flexible lead body and at least one electrode. The method includes applying a layer of poly vinylidene fluoride on the flexible lead body. Optionally, applying the layer of poly vinylidene fluoride includes heat shrinking a tube of poly vinylidene fluoride on the flexible lead body. In another embodiment, the method further includes applying a second layer of insulation, wherein the second layer of insulation is silicone rubber.
The lead and method provides abrasion resistance, lubricity, and resistance to body fluids. In addition poly vinylidene fluoride has a heat shrink temperature which does not damage the lead and does not degrade a layer of silicone on the lead.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention.
The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.